A common drive system for certain types of vehicles includes the ability to shift from two-wheel drive to four-wheel drive. Either the front wheels or the back wheels are permanently engaged with the vehicle's drive train and the remaining set of wheels is shifted into and out of engagement with the drive train. For purposes of discussion, the rear wheels will hereafter be considered permanently engaged with the drive train and the front wheels are in part-time engagement, but the reader will appreciate that the invention is equally applicable to the front wheels being permanently engaged with a drive train and the rear wheels in part-time engagement.
Whereas a drive train will include a transmission that transmits drive power from the vehicle's engine to a propeller shaft that extends to the differential and then the wheel axles, e.g, of the rear wheels, in order to provide four-wheel drive, there is a further propeller shaft that extends forward to the differential of the front wheels, e.g., via a transfer case that also receives drive power from the transmission. A shift mechanism in the transfer case engages and disengages the drive power to the propeller shaft for the front wheels.
In the disengaged position, the front wheels are not being driven but then the passive turning of the front wheels drives the front wheel axles and front wheel propeller shaft unless there is also a disconnect mechanism between each front wheel and its axle. It is the disconnect mechanism between the wheel and axle to which the present invention is primarily directed although those skilled in the art will appreciate the further application of the invention, e.g., to other components of the drive train.
Returning to the front wheel connect/disconnect mechanism, historically this mechanism was located in the wheel hub and advanced from manual to automatic operation. The structural arrangement included a cylindrically configured spindle which was fixedly mounted to the vehicle chassis, i.e., on the steering knuckle. The axle protruded through the center of the spindle and a wheel hub was mounted on the exterior of the spindle and surrounding the axle. Each of the wheel hub and axle was independently rotatable relative to the spindle and a clutch mechanism at the outboard end of the spindle produced the desired connect/disconnect of the wheel hub to the axle. A later version referred to as a live spindle provided for the spindle to be rotatably mounted to the vehicle chassis and the wheel hub was fixedly mounted to the spindle. The axle as before was protruded through the spindle and a clutch mechanism at the outboard end of the spindle produced the connect/disconnect operation.